[Maps] fix tile layer attibution text and attribution link validation errors

x-pack/plugins/maps/public/classes/sources/xyz_tms_source/layer_wizard.tsx

@@ -19,7 +19,12 @@ export const tmsLayerWizardConfig: LayerWizard = {
   }),
   icon: 'grid',
   renderWizard: ({ previewLayers }: RenderWizardArguments) => {
-    const onSourceConfigChange = (sourceConfig: XYZTMSSourceConfig) => {
+    const onSourceConfigChange = (sourceConfig: XYZTMSSourceConfig | null) => {
+      if (!sourceConfig) {
+        previewLayers([]);
+        return;
+      }
+
       const layerDescriptor = TileLayer.createDescriptor({
         sourceDescriptor: XYZTMSSource.createDescriptor(sourceConfig),
       });

x-pack/plugins/maps/public/classes/sources/xyz_tms_source/xyz_tms_editor.test.tsx

@@ -0,0 +1,37 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+import React from 'react';
+import { shallow } from 'enzyme';
+import { XYZTMSEditor } from './xyz_tms_editor';
+
+const onSourceConfigChange = () => {};
+
+test('should render', () => {
+  const component = shallow(<XYZTMSEditor onSourceConfigChange={onSourceConfigChange} />);
+  expect(component).toMatchSnapshot();
+});
+
+describe('attribution validation', () => {
+  test('should provide validation error when attribution text is provided without attribution url', () => {
+    const component = shallow(<XYZTMSEditor onSourceConfigChange={onSourceConfigChange} />);
+    component.setState({ attributionText: 'myAttribtionLabel' });
+    expect(component).toMatchSnapshot();
+  });
+
+  test('should provide validation error when attribution url is provided without attribution text', () => {
+    const component = shallow(<XYZTMSEditor onSourceConfigChange={onSourceConfigChange} />);
+    component.setState({ attributionUrl: 'http://mySource' });
+    expect(component).toMatchSnapshot();
+  });
+
+  test('should provide no validation errors when attribution text and attribution url are provided', () => {
+    const component = shallow(<XYZTMSEditor onSourceConfigChange={onSourceConfigChange} />);
+    component.setState({ attributionText: 'myAttribtionLabel' });
+    component.setState({ attributionUrl: 'http://mySource' });
+    expect(component).toMatchSnapshot();
+  });
+});